Bimetal Silver Contact

Ag/Cu Composite Structure and Material Selection
A bimetal silver contact consists of two functional metal layers: a silver or silver alloy contact layer and a copper or copper alloy base.

The silver layer forms the electrical contact surface. Its material composition determines important properties such as electrical conductivity, arc erosion resistance, welding resistance, and mechanical hardness. The copper substrate provides a conductive base, mechanical support, and a pathway for heat dissipation.

Apollo offers different silver contact material combinations according to the intended switching conditions.

Material selection should consider rated current, operating voltage, AC/DC switching conditions, switching frequency, and contact pressure. Silver alloy composition should be matched to the actual electrical duty rather than selected solely by material price.

Silver Layer Thickness and Copper Substrate Design
The silver layer thickness directly affects the available contact material and the service life of the working contact surface.

A thicker silver layer can provide more material allowance for wear and arc erosion, but the correct value depends on the switching duty, contact geometry, and required service life. The copper base thickness must also provide sufficient mechanical strength and dimensional stability during riveting and assembly.

For reference, Apollo's published technical information identifies a typical composite structure with a silver alloy layer of approximately 0.3–1.0 mm and a copper base of approximately 0.5–5 mm for applicable designs. These are design reference ranges, not universal limits for every product.

One-die Two-punch Cold Heading
Apollo's bimetal contact production uses a composite cold-heading approach in which silver alloy wire and copper wire are fed into a forming process to create a two-layer contact structure.

A typical production sequence is:
1. Silver alloy and copper wire preparation.
2. Material feeding and alignment.
3. One-die, two-punch composite cold heading.
4. Contact head forming and dimensional correction.
5. Cleaning and annealing where specified.
6. Final dimensional and appearance inspection.

During cold heading, material deformation and interface contact conditions must be controlled to maintain consistent silver-layer distribution and composite bonding.

Tooling design should consider wire diameter, feed length, punch geometry, forming pressure, material hardness, and finished contact dimensions.

Bimetal Silver Contact Specifications

Dimensional Control and Forming Accuracy
Bimetal contact dimensions must remain consistent throughout production because the finished rivet geometry affects assembly fit, contact pressure, and electrical connection stability.

Critical dimensions generally include:
Contact head diameter.
Silver layer thickness.
Total rivet length.
Copper base diameter.
Head height and curvature.
Concentricity between the silver layer and copper base.
Burr condition and edge profile.

Tolerance requirements should be specified on the customer drawing. For critical dimensions, optical measurement and calibrated dimensional inspection can be used to verify first-article samples and production batches.

For projects requiring different contact structures, see Solid Silver Contacts and compare the material configuration with bimetal contacts.

Metallurgical Bonding Between Silver Alloy and Copper
The primary manufacturing requirement for a bimetal silver contact is a stable interface between the silver alloy layer and copper substrate.

Unlike an electroplated silver contact, a bimetal contact uses a relatively thick silver alloy layer that is integrated with the copper base through a composite forming process.

The interface must withstand subsequent manufacturing operations, including riveting, welding, and assembly. Inadequate bonding can lead to separation or cracking during forming and service.

The main process control points include:
Surface cleanliness before composite forming.
Consistent alignment of silver and copper materials.
Controlled material deformation.
Stable forming pressure and punch geometry.
Inspection of interface continuity.
Verification of the finished contact profile.

The purpose is to produce a composite contact that maintains its material structure during assembly and electrical operation.

Bimetal Contact vs. Silver-Plated Contact
These two products should not be treated as the same component.

For applications where silver coating is specified instead of a composite silver layer, review Silver Plated Contacts.

Contact Surface Preparation and Cleaning
The contact surface must be free from oil, loose particles, excessive oxidation, and forming residues that may interfere with electrical contact.

Cleaning requirements should be established according to the contact alloy, storage conditions, and subsequent assembly process.

Inspection should cover:
Contact surface appearance.
Burrs and edge defects.
Oil and particulate contamination.
Oxidation and discoloration.
Dimensional deformation during cleaning and handling.

Bimetal silver contacts are generally supplied with a clean contact surface. Additional plating should only be applied where specified by the design and validated for the intended application.

Request Custom Technical Evaluation

Bimetal silver contact inspection must verify more than the external appearance of the finished rivet. The silver layer, copper substrate, composite interface, and contact geometry all contribute to the electrical and mechanical performance of the finished component.

Apollo has manufactured electrical silver contacts and related components since 1990. Its product range includes solid silver contacts, bimetal contacts, trimetal contacts, plated contacts, and contact assemblies for low-voltage electrical equipment.

Incoming Material Inspection
Incoming inspection should verify the material grade and condition of silver alloy and copper wire.

Key inspection items include:
Silver alloy composition and material identification.
Copper base material grade.
Wire diameter and dimensional consistency.
Material surface condition.
Supplier material certificates.
Batch identification and traceability.

Composite Interface Inspection
The silver-copper interface is a critical quality characteristic of bimetal contacts.

Depending on the product specification, inspection can include:
Cross-sectional metallographic examination.
Silver layer thickness measurement.
Interface continuity inspection.
Bonding integrity evaluation.
Visual examination for cracks, voids, and separation.

Metallographic analysis provides direct evidence of the composite interface and silver-layer distribution.

Electrical Performance Testing
Electrical performance should be evaluated under defined contact force, current, voltage, and measurement conditions.

Recommended inspection items include:

Quality Management and Production Documentation
Apollo's website identifies ISO 9001:2015 quality management and RoHS-related material compliance information. Customer-specific documentation should be agreed upon according to the product and purchasing requirements.

For automotive and electrical equipment programs, the quality documentation package can be discussed at the project quotation stage, including:

Material inspection records.
First Article Inspection Report.
Dimensional inspection report.
Process Flow Diagram.
PFMEA.
Control Plan.
CPK analysis where applicable.
PPAP Level 3 documentation where required by the customer.

IATF 16949 certification should only be stated where the relevant manufacturing entity and production scope are covered by a valid certificate. It should not be presented as a default certification claim for this category.

Batch Consistency and Supply Support
For high-volume electrical contact production, consistent silver layer thickness, contact geometry, and composite bonding are essential to assembly stability.

Apollo supports customized contact dimensions and drawing-based manufacturing. Its published product information also lists sample availability and OEM/ODM production support. Delivery and sampling schedules should be confirmed according to tooling status, material availability, and order volume.

Ag/Cu composite contacts require controlled material selection, silver layer distribution, and interface integrity.

Send your 2D drawings, 3D CAD files, or existing contact samples to Apollo's engineering team for manufacturing evaluation.

To speed up the review, please include:
Silver alloy specification: Ag, AgNi10, AgSnO₂, or other grades.
Copper substrate material and dimensions.
Required silver layer thickness.
Contact diameter, head profile, and rivet length.
Rated current, operating voltage, and switching frequency.
Required contact resistance and mechanical test criteria.
Annual demand and expected production volume.

Apollo can evaluate composite forming feasibility, material utilization, dimensional requirements, and inspection methods before tooling confirmation.

Submit your.STEP, .DWG, or PDF drawings to request a preliminary DFM review and a factory-direct quotation. A 24-hour response target can be arranged for complete inquiries, subject to technical complexity.

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